Stress and weight loss don't mix well. The first goal should be to take a stress free approach to your diet. Have confidence in yourself and keep your motivation. This is a very important starting point in the goal of weight loss
First off...
Set a realistic weight loss goal. Don't try and lose 50 pounds in a week. This wont happen. instead, focus on an overall goal like 50 pounds. Then give yourself monthly goals to accomplish this task.
The more time you give yourself the less stress you will feel. If you are losing the weight ahead of schedule then Great! The objective here is to keep it as stress free as possible while u lose the weight.
Second...
Make a list of all the foods you eat. Now cut out any foods with excessive sugars. Things like high fructose corn syrup will not help you lose weight. You need to eliminate them completely from your diet.
Try and use sugar substitutes when necessary. Also watch out for unsaturated fats. Stay away from alcohol and fast food as well. Abstaining from all these things will speed your fat loss.
Third...
Keep track of your calorie intake. This can help you understand what you would eat on your normal diet. Now trim 500 calories off your original diet. This can easily help you lose up to a pound a week.
Counting calories can be very useful when first starting out on a diet. They can help you put yourself on the right track to weight loss. Once you have established a good routine you can continue without this step.
Conclusion
Remember keep it stress free! The less you have to worry about, the more weight you will lose. This is a great way to diet. Help yourself remain focused on motivated by keeping track of what you eat as well.
There are many good systems and books out there that further expand on these principles. I found when first starting to lose weight it helped me to follow some of these systems.